Surgical manipulator

ABSTRACT

The present invention provides a surgical manipulator which capable of manipulating a surgical or medical tool in up to six degrees of freedom. The manipulator has a relatively lightweight, compact design as a result of the use of high force to mass ratio actuators. The manipulator includes a mounting fixture which permits the manipulator to be fixed relative to a portion of a body of a patient.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/261,940, which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to manipulators and, more particularly toa manipulator suitable for use in medical procedures, including surgicalprocedures.

BACKGROUND OF THE INVENTION

Conventional devices which are used to perform very complex and/orphysically demanding surgical procedures like neurosurgery, spinesurgery, ear surgery, head and neck surgery, hand surgery and minimallyinvasive surgical procedures have a number of drawbacks as it relates tothe dexterity of the surgeon. For example, the surgeon can easily becomefatigued by the need to manually support the surgical device during itsuse. Additionally, the surgeon may have to orient his hands in anawkward position in order to operate the device. Furthermore,conventional devices used in such surgical procedures can produceangular magnification of errors. As a result, a surgeon has considerablyless dexterity and precision when performing an operation with suchsurgical devices than when performing an operation by traditionaltechniques in which the surgeon grasps a tool directly.

Accordingly, there is an increasing interest in the use of poweredmanipulators, such as robotic and master-slave manipulators forsupporting and manipulating surgical tools during medical procedures.Such manipulators can provide a number of advantages to both patientsand medical practitioners. In particular, a master/slave controlledmanipulator can enhance the dexterity of the surgeon/operator so as toallow the surgeon to manipulate a medical tool with greater dexteritythan he could if he was actually holding the tool in his hands. Amanipulator can also reduce the fatigue experienced by a surgeon, sinceit eliminates the need for the surgeon to physically support the medicaltool or device during its use. Additionally, the surgeon can let go ofthe manipulator and perform other tasks without the medical toolundergoing movement, which increases the efficiency of the surgeon andcan reduce the number of individuals that are necessary to perform aparticular procedure. Thus, manipulators can allow medical procedures tobe performed much more rapidly, resulting in less stress on the patient.

However, the use of such powered manipulators can impose certain safetyproblems. In particular, movement of the patient relative to themanipulator during the surgical or other interventional procedure canlead to serious trauma. Thus, it is generally thought that a patientmust be under a general anesthesia or other paralytic during a procedurethat is performed using a powered manipulator. Powered manipulators aregenerally thought as unsuitable for use in awake procedures. The use ofa general anesthesia including neuro-muscular paralysis or the like,however, introduces more risk into the procedure and does not completelysolve the problem of movement of the patient relative to themanipulator. For example, even when under a general anesthesia patientmotion can be caused by respiration, cardio-ballistic motion,involuntary muscle motion (e.g., myoclonic jerks, tremors, twitching),peristalsis and inadvertent contact with the patient.

OBJECTS AND SUMMARY OF THE INVENTION

Accordingly, in view of the foregoing, a general object of the presentinvention is to provide an improved manipulator for use in surgical andother interventional medical procedures.

A more specific object of the present invention is to provide a surgicalmanipulator that can enhance the dexterity and precision of asurgeon/operator.

A further object of the present invention is to provide a surgicalmanipulator that provides enhanced patient safety by substantiallyreducing the likelihood of movement of the patient relative to themanipulator.

Another object of the present invention is to provide a surgicalmanipulator that is capable of achieving enhanced registration precisionfor image guided procedures or for use of anatomic waypoints (fiducials)identified during surgery.

These and other features and advantages of the invention will be morereadily apparent upon reading the following description of a preferredexemplary embodiment of the invention and upon reference to theaccompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front perspective view of an illustrative manipulatorconstructed in accordance with the teachings of the present invention.

FIG. 2 is a rear perspective view of the manipulator of FIG. 1.

FIG. 3 is a block diagram of an illustrative control system for amanipulator constructed in accordance with the teachings of the presentinvention.

FIG. 4 is a perspective view of an alternative embodiment of amanipulator constructed in accordance with the present inventionsupporting a cautery/dissection tool.

FIG. 5 is a perspective view of the manipulator of FIG. 4 supporting adrill.

FIG. 6 is a perspective view of the manipulator of FIG. 4 mounted to ahead clamp fixation system.

FIG. 7 is another perspective view of the manipulator of FIG. 4 mountedto a head clamp fixation system.

FIG. 8 is a perspective view of the manipulator of FIG. 4 furtherincluding a position tracking mechanism which is illustratedschematically.

While the invention will be described and disclosed in connection withcertain preferred embodiments and procedures, it is not intended tolimit the invention to those specific embodiments. Rather it is intendedto cover all such alternative embodiments and modifications as fallwithin the spirit and scope of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now more particularly to FIG. 1 of the drawings there is shownan illustrative embodiment of a surgical manipulator 10 constructed inaccordance with the present invention. The illustrated manipulator 10can interchangeably support and move a medical tool 12 with up to sixdegrees of freedom. As will be appreciated, the invention is not limitedto any particular type of medical tool rather any suitable tool can beused with the manipulator including, but not limited to, needle holders,staple or clamp appliers, probes, scissors, forceps, cautery, suctioncutters, dissectors, drills, lasers, ultrasonic devices and diagnosticdevices. The tools can be reusable, limited reuse or disposable. If themedical tool has moving parts that are conventionally human powered, themanipulator 10 can be adapted to accommodate an actuator dedicated topowering the tool such as for example an electric, pneumatic orhydraulic actuator.

In order to provide dexterity enhancement for an operator/surgeon inperforming surgical and certain interventional radiology procedures, themanipulator 10 can be used as a slave robot in a master-slave roboticsystem. In such a system, a surgeon/operator provides position inputsignals to the “slave” manipulator via a master or haptic interface 13which operates through a controller 15 or control console as in theschematic block diagram of FIG. 3. Specifically, through the use of aninput device 17 on the haptic interface 13 such as a six degree offreedom tool handle with force feedback, joystick, foot pedal or thelike, the surgeon indicates the desired movement of the tool 12 held bythe manipulator 10. The haptic interface 13 relays these signals to thecontroller 15, which, in turn, applies various desired predeterminedadjustments to the signals prior to relaying them to the slavemanipulator. Any haptic interface having an equal or greater number ofdegrees of freedom (DOF) than the manipulator can be used to control themanipulator via the controller. Examples of haptic interfaces or masterswhich can be used with the present invention include the Freedom 6Savailable from MPB Technologies of Montreal, Canada, and other hapticinterfaces commercially available from Sensable Technology of Cambridge,Mass. and MicroDexterity Systems of Albuquerque, N. Mex.

Based on the signals provided by the controller 15, the manipulator 10executes the desired movement or operation of the tool 12. Thus, anydesired dexterity enhancement can be achieved by setting up thecontroller 15 to perform the appropriate adjustments to the signals sentfrom the haptic interface 13. For example, this can be accomplished byproviding the controller 15 with software which performs a desireddexterity enhancement algorithm. Software dexterity enhancementalgorithms can include position scaling (typically downscaling), forcescaling (up-scaling for bone and cartilage, downscaling for softtissue), tremor filtering, gravity compensation, programmable positionboundaries, motion compensation for aneurysms, velocity limits (e.g.,preventing rapid movement into brain, nerve or spinal cord tissue afterdrilling through bone), and, as discussed in greater detail below, imagereferencing. These and other examples of possible algorithms are wellknown in the field of robotics and described in detail in publishedliterature. An example of a suitable controller for use in the presentinvention is the Turbo PMAC available from Delta Tau Data Systems ofNorthridge, Calif.

To permit movement of the tool 12 with, in the illustrated embodiment,six degrees of freedom, the tool is supported at a lower end of a toolsupport shaft 14 that can be translated in space via a system of rotaryand linear actuators. More specifically, in the illustrated embodiment,the tool support shaft 14 is supported by a pair of, in this case,vertically spaced support or control arms 16, 18 each of which isindependently movable via a respective linear actuator 20, 22 and arespective rotary actuator 24, 26. As shown in FIGS. 1 and 2, the linearactuator 20, 22 associated with each control arm 16, 18 is arranged soas to translate its respective control arm in a telescoping manner in alengthwise direction. Each linear actuator 20, 22 is connected, in turn,to the output shaft of its corresponding rotary actuator 24, 26 so as topermit pivotal movement of the linear actuators 20, 22, and thereby thecontrol arms 16, 18. In this case, the rotary actuators 24, 26 arearranged in stacked relation on a stationary support frame 28 such thattheir rotational axes are aligned. The rotary actuators, however, do nothave to be in stacked relation as the two actuators 24, 26 can beindependently located relative to each other.

Through the combination of the control arms 16, 18 and theircorresponding linear 20, 22 and rotary actuators 24, 26, the toolsupport shaft 14 can be moved in space in four degrees of freedom. Forexample, the manipulator 10 can operate as a differential mechanism inthat relatively large pitch and yaw angles of the tool support shaft 14can be produced by rotating the rotary actuators 24, 26 for the twocontrol arms 16, 18 in opposite directions and by moving the linearactuators 20, 22 for the two control arms in opposite directions.Additionally, the tool support shaft 14 can be moved like a cylindricalor polar coordinate robot by rotating the rotary actuators 24, 26 forthe two control arms 16, 18 in the same direction and by moving thelinear actuators 20, 22 for the two control arms in the same direction.

For moving the tool 12 in the lengthwise direction of the tool supportshaft 14 and to provide for rotation of the tool about the longitudinalaxis of the tool support shaft, two additional actuators are provided.In particular a linear actuator 30 is incorporated into the tool supportshaft 14 which is operatively connected to the tool 12 (via a shaft orother means) so as to permit lengthwise movement of the tool 12 in atelescoping manner relative to the longitudinal axis of the tool supportshaft 14. This lengthwise movement of the tool 12 relative to the toolsupport shaft 14 can be used to insert and withdraw the tool 12 from thebody of a patient. The rotary movement of the tool 12 is produced by arotary actuator 32 arranged, in this case, at the upper end of the toolsupport shaft 14 and operatively connected to the tool 12 (again, via ashaft or other suitable means) so as to enable rotation of the tool 12about the longitudinal axis of the tool support shaft 14. The rotarymovement of the tool 12 relative to the tool support shaft 14 can beuseful when using axially asymmetric tools, such as for example,scissors which extend at an angle with respect to the tool supportshaft.

To permit movement of the tool support shaft in the desired degrees offreedom each control arm 16, 18 is connected to the tool shaft 14 usingan appropriate universal or gimbals joint. In the illustratedembodiment, the joints between the control arms and the tool supportshaft comprise three degree of freedom Hookes type joints 34, 36. Thejoints between the tool support shaft and the control arms shouldprovide six degrees of freedom to the tool shaft. This can also beaccomplished by providing one joint which has two degrees of freedom anda second joint which has four degrees of freedom. Additionally, twojoints each having two degrees of freedom could be used with the toolshaft itself supplying the two additional degrees of freedom to the toolas shown in FIGS. 1 and 2.

For sensing the positions of the various linear and rotary actuators 20,22, 24, 26, 30, 32 and, in turn, the control arms 16, 18, joints 34, 36and tool support shaft 14, the actuators can be equipped with positionsensors 50. Each of the linear and rotary actuators can be incommunication with the controller and the position sensors can provideposition information in a feedback loop to the controller as shown inFIG. 3. For ease of reference, the position sensor for only one of theactuators is shown in FIG. 3. In one preferred embodiment, opticalencoders are used to sense the positions of the various actuators,however, it will be appreciated that any number of differentconventional position sensors can be used. Likewise, the variousactuators can also be equipped with force sensors 52 (again, only one ofwhich is shown in FIG. 3) for sensing the forces or torques applied bythe actuators so as to enable a determination of the forces and torquesapplied to the tool support shaft 14. As shown in FIG. 3, thisinformation can again be provided in a feedback control loop to thecontroller 15, for example to allow force feedback to the input deviceof the haptic interface (shown schematically as line 56). Of course, anyknown method for measuring forces and/or torques can be used, including,for example, foil type or semiconductor strain gauges or load cells.

Another embodiment of a manipulator according to the invention is shownin FIGS. 4 and 5 wherein components similar to those described abovehave been given similar reference numerals in the 100 series. Themanipulator 110 of FIGS. 4 and 5 is very similar in configuration andoperation to that of the manipulator 10 shown in FIGS. 1 and 2. Inparticular, the manipulator 110 shown in FIGS. 4 and 5 can move a tool112 supported on a tool support shaft 114 in six degrees of freedom. Tothis end, as with the FIGS. 1 and 2 embodiment, the tool support shaft114 is supported by a pair of spaced control arms 116, 118 each of whichis independently movable via a respective linear actuator 120, 122 and arespective rotary actuator 124, 126. The linear actuator 120, 122associated with each control arm 116, 118 translates the control arm inits lengthwise direction while the rotary actuator 124, 126 can pivotthe linear actuator and, in turn, the control arm. The manipulator 110shown in FIGS. 4 and 5 also includes a linear actuator 130 on the toolsupport shaft 114 which facilitates tool insertion and withdrawal and arotary actuator 132 on the tool support shaft which facilitates toolroll.

Unlike the manipulator shown in FIGS. 1 and 2, the rotary actuators 124,126 are supported on a frame 128 such that their rotary axes are notaligned. The support frame 128, in this case, includes upper, lower andintermediate support arms 129 between which the rotary and linearactuators are supported. The illustrated support frame 128 provides arelatively compact arrangement which can be readily connected toexisting mounting arrangements as described in greater detail below.

FIGS. 4 and 5 also illustrate how the manipulator of the presentinvention can be used to support different tools. Specifically, as shownin FIG. 4, the manipulator 110 can support a tool 112, in theillustrated embodiment a cautery/dissection tool, which is arrangedcoaxially with the tool support shaft 114. Alternatively, as shown inFIG. 5, a tool 112 (in this instance, a drill) can be supported inoffset relation from the tool support shaft 114 in order to accommodate,for example, an actuator for a powered tool. In this case, the tool 112is connected to the tool support shaft 114 via a connector piece 144which permits the tool to be moved in space with the support shaft.Moreover, by connecting the tool 112 to the pivotable and extensiblelower end of the support shaft 114, the tool can also be moved via thetool insertion linear actuator 130 and the tool roll rotary actuator 132on the support shaft. As will be appreciated, other arrangements can beused to mount the tool on the tool support shaft.

The construction and operation of the illustrated manipulators issimilar to several of the manipulator embodiments disclosed in commonlyassigned PCT Application Serial No. PCT/US99/27650 and correspondingU.S. application Ser. No. 09/856,453 entitled “Surgical Manipulator” thedisclosure of which is incorporated herein by reference. As will beappreciated, while the illustrated manipulator geometry provides certainadvantages including movement in six degrees of freedom, the presentinvention is not limited to a particular manipulator architecture orkinematic scheme. Instead, all that is necessary is to provide amanipulator that is capable of moving a tool in a desired number ofdegrees of freedom. For example, other manipulator architectures andkinematic schemes that can be used include a so-called dual SCARA schemesuch as disclosed in PCT Application Serial No. PCT/US99/27650 and U.S.application Ser. No. 09/856,453 and a dual planar scheme such asdisclosed in U.S. Pat. Nos. 5,943,914 and 6,000,297 entitledrespectively “Master-Slave Micromanipulator Apparatus” and “Master-SlaveMicromanipulator Method”. Moreover, while the illustrated embodimentonly includes a single manipulator, two or more manipulators may beprovided such as for procedures which require more than one hand or arm.

In accordance with one important aspect of the present invention, tosubstantially reduce the likelihood of patient movement relative to themanipulator 10, 110 during a surgical or other interventional procedure,thereby enhancing patient safety, the manipulator 10, 110 can include amounting fixture which permits the manipulator to be fixed relative toat least a particular portion of a patient's body. The ability to fixthe manipulator 10, 110 relative to the patient's body potentiallyeliminates the need for general anesthesia and muscle paralytics, andthe associated medical risks, as well as the need for active complianceand/or passive backdriveabilty of the manipulator actuators.

To this end, in the embodiment illustrated in FIGS. 1 and 2, theactuator support frame 28 and, in turn, the tool support shaft 14 areconnected to a mounting structure 37, in this instance a mounting ring38, which can be mounted directly to skull or other body part of apatient. To facilitate attachment of the mounting ring 38 to, forinstance, the skull of the patient, the mounting ring 38 includesmounting holes 40 (three in the illustrated embodiment) which canreceive screws that attach the mounting ring to the skull. The actuatorsupport frame 28 is connected to the mounting ring 38 by a clampingmechanism 42 which permits the actuator support frame 28 to be moved andlocked into any given position around the perimeter of the mounting ring38.

An embodiment of the invention in which the mounting structure includesa head clamp fixation system is illustrated in FIGS. 6 and 7. In theillustrated embodiment, an arm 160 is provided which interconnects thesupport frame 128 of the manipulator 110 of FIGS. 4 and 5 with a headclamp 162. The clamp 162 includes a C-shaped frame 164 which supports afirst fixed head engaging pin 166 on one side and second and third headengaging pins 168, 170 on the opposite side. The second and third headengaging pins 168, 170 are supported on a clevis 172 that is rotatablerelative to the frame 164 so as to allow a surgeon to adjust the angularposition of the patient's head relative to the frame 164. The clamp 162includes a rotation mechanism 174 for releasably locking the clevis 172in a particular angular position relative to the frame 164. In theillustrated embodiment, the head clamp 162 is supported by a base unit176 which allows the head clamp to be mounted to a medical table.

To ensure that the manipulator 110 remains fixed relative to thepatient's head during adjustment of the position of the head, the arm160 supporting the manipulator is tied into the rotation mechanism 174of the clamp 162. In particular, the arm 160 is tied into a sleeve 178which rotates with the clevis 172 as the angular position of the clevisis adjusted via a knob 180 on the rotation mechanism 174. Thus, themanipulator 110 remains fixed in the same position relative to theclevis 172, and in turn the patient's head, during any adjustment of thehead. One example of a head clamp fixation system that can be used inthe present invention is sold under the tradename MAYFIELD® by OhioMedical Products of Cincinnati, Ohio (see, e.g. U.S. Pat. No. 5,269,034and U.S. Pat. No. 5,546,663).

Of course, as will be appreciated by those skilled in the art, thepresent invention is not limited to any particular mounting fixture, butrather extends to any mounting fixture or system which allows themanipulator to be fixed relative to a desired portion of the patient'sbody. Nor is the present invention limited to being mountable to anyparticular location on the body. For instance, the manipulator 10 can bemounted to the skull (e.g., to perform neurosurgery, ear surgery ornasal surgery), the spine or other bony structures.

In order to permit mounting of the manipulator 10 to a patient, themanipulator 10 must have a relatively lightweight, compact design thathas a relatively low inertia. Utilizing a lightweight, compactmanipulator, helps alleviate the need to provide alternative supportstructures to relieve some of the weight exerted on the patient. Whilesuch support structures help reduce some of the stress on the patientcaused by a manipulator, they can introduce significant inertiaproblems. To achieve the low mass and inertia, linear and rotaryactuators having a relatively high force to mass ratio should be used inthe manipulator. To this end, in one presently preferred embodiment ofthe invention, the linear and rotary actuators (20, 22, 24, 26, 120,122, 124, 126) used in the manipulator comprise ultrasonic motors.

Besides a very high force to mass ratio, ultrasonic motors provideseveral other advantages over conventional stepper and DC motors. Forexample, ultrasonic motors have intrinsic braking when powered down at aforce equivalent to its force when moving. This provides increasedpatient safety. Ultrasonic motors do not have heat dissipation issuesand can be isolated electrically. Moreover, ultrasonic motors are verystable so as to permit use in clean rooms. Additionally, as compared topneumatic actuators, actuators based on ultrasonic motors do not haveovershoot problems when the tool is used to apply a force on a rigidbody which then breaks free. One example of an ultrasonic motor suitablefor use as either a linear or rotary actuator in the present inventionis the SAW Ultrasonic Motor available from Nanomotion of Yokeneam,Israel (described in U.S. Pat. No. 5,453,653).

Alternatively, electrodynamic motors, hydraulic actuators or cabledrives could also be used as the linear and rotary actuators on themanipulator. With respect to cable drives, either rotary or push-pullcould be used. The prime movers for the cables can include air or fluidturbines or servo motors. When using cable drives, significant torqueamplification would have to take place through the controller in orderto compensate for the effects of backlash, windup, hysteresis and cablefriction. If hydraulic actuators are used for the linear and rotaryactuators, water, saline, or perfluorocarbon liquids can be used forhydraulic actuation to ensure patient safety in the event the hydraulicfluid comes into contact with the patient. Gear pumps or other suitablepumps like peristaltic, diaphragm, piston and venturi pumps can be usedto control the flow of hydraulic fluid which is relativelyincompressible compared to pneumatic actuation thereby avoidingovershoot problems. The actuators themselves can comprise, for example,piston/cylinder actuators (linear actuators), rotary vane, diaphragm andBourdon tubes. To reduce static and dynamic friction, hydrostaticbearings can be used for the rotary and linear actuators. Other types ofactuators having high force to mass ratios could also be used.

According to a further aspect of the present invention, the capabilityof fixing the manipulator 10, 110 relative to the patient also canprovide enhanced precision of the registration of the manipulator 10 andthe tool 12, 112 with respect to the patient. In particular, fixing themanipulator 10, 110 relative to the patient provides a constantmechanical reference so that images or constant subsets of image dataacquired prior to or earlier in the procedure will remain in the sameposition relative to the manipulator 10, 110 as the procedureprogresses.

With the embodiment of the invention shown in FIGS. 1 and 2, one methodby which this can be accomplished is to perform preoperative imaging(e.g., magnetic resonance (MR) or X-ray) with the screws to be used tofix the manipulator 10 to the patient already implanted in the patient.The screws, which can be made of a MR or X-ray compatible material, canthen act as reference points or fiducials in the images. At the time ofsurgery, the screws are used to define the mounting points for themanipulator mounting ring 38. Then, as the operation is performed, theposition of the tool 12 can be rendered against the preoperative image.If desired, during the procedure, the image data against which theposition of the tool 12 is rendered can be updated using, for example,CT, MR or the like.

As an alternative to performing the preoperative imaging with themounting screws in place, the position of the tool 12, 112 and themounting structure or the manipulator mechanism 10, 110 can be trackedrelative to a pre- or intra-operative image using optical triangulationby integrating the manipulator into a StealthStation® system availablefrom Medtronic of Minneapolis, Minn. or by using another threedimensional, six degree of freedom position sensing technology wellknown in the field of neuro, spine and other types of surgery such as,for example, electromagnetic tracking.

An electromagnetic tracking or guidance system can be based, forexample, on sensitivity to magnetic field strength, phase delay, phaseversus position or pulse time of travel measurements to calculate aposition and orientation of the tool with any degree of certainty fromone to six degrees of constraint. One way in which this can beaccomplished is to use an electromagnetic field generator 90 comprising,for example, three orthogonally disposed coil loops which are capable ofproducing a multidimensional field in three dimensions such as shownschematically in FIG. 8. The magnetic fields produced by each of thethree coils can be mutually distinguishable from one another via eitherphase, frequency or time multiplexing. Remote sensors 92 for detectingthe field generated by the field generator, which could comprise threeorthogonally disposed dipole sensing elements, can be placed on the tooland in other locations such as on the manipulator as shown in FIG. 8.The position of the remote sensors 92 relative to the field generator 90can then be monitored and correlated with stored preoperative images bya position detection controller 94 and shown on a display 96. Theposition detection controller could be the same controller used tocontrol movement of the manipulator or a different controller.

These types of electromagnetic positioning techniques are used withglobal positioning systems, radar, resolvers and other electromagneticposition determining systems. Such an electromagnetic tracking orguiding system is not limited to use with the particular manipulatorconfigurations disclosed herein but rather can be used to track and/orguide any type of tool that is supported and moved a manipulator orrobot in one or more degrees of freedom. Electromagnetic positionsystems that can be adapted for use with the present invention areavailable from Visualization Technologies of Boston, Mass. (see, e.g.,U.S. Pat. No. 5,676,673 and U.S. Pat. No. 5,829,444), UltraGuide ofLakewood, Colo. and Polhemus of Colchester, Vt.

During a medical procedure, it is possible that the manipulator 10, 110and haptic interface 13 will be tilted or rotated with respect to oneanother such that they are in different orientations with respect to thepatient. For example, the patient may be placed in a specificorientation in order to allow viewing of the surgical site with, forexample, a microscope. The manipulator 10, 110 will then be arranged soas to provide the best access to the surgical site without obscuring theview of the surgical site. The haptic interface, in turn, will beoriented to provide a good ergometric and comfortable position for thesurgeon's hand arm. In such a case, it is likely that the coordinatereference frames of the manipulator and haptic interface will be skewedfrom one another and with respect to the patient.

The surgeon operating the manipulator through the haptic interface willbe observing the tool 12 held by the manipulator 10, 110 and thesurgical site during a surgical procedure. Accordingly, the positiontracking system (which can be electromagnetic, optical or any othersuitable system) and accompanying position detection controller can beadapted to specifically locate the manipulator, haptic interface andpatient and to perform any necessary translations of movements in thehaptic interface reference frame and manipulator reference frame withrespect to the coordinate reference frame of the patient. Thesetranslations can be performed, for example, by a translation algorithmexecuted by the controller and can coordinate movement of the hapticinterface input device and the tool held by the manipulator with respectto the patient's frame of reference regardless of the orientation of thehaptic interface and manipulator relative to each other and the patient.Thus, when a surgeon moves his hand forward straight and level using thehaptic interface, the medical tool held by the manipulator will alsomove in the same trajectory even if the manipulator is mounted in askewed orientation relative to the patient.

In accordance with yet another aspect of the present invention, themanipulator 10, 110 can be constructed so as to be compatible with an MRor X-ray environment. This would allow the manipulator 10 to operatewithin and during a MR imaging or other X-ray procedure, therebyenabling the surgeon to visualize, for example, the target tissue,normal tissue and the tool 12, 112 in the same real-time or nearreal-time imaging environment. In order to allow the manipulator 10, 110to operate in a MR environment, the manipulator must be constructedentirely of MR imaging compatible materials such as certain metals,plastics, glass and ceramics. Additionally, the linear and rotaryactuators 20, 22, 24, 26, 120, 122, 124, 126 used in the manipulatormust also be compatible with MR imaging. In this regard, both ultrasonicand hydraulic actuators have the additional advantage of being MRcompatible. In order to permit the manipulator 10, 110 to be used whileperforming X-ray imaging, certain components of the manipulator can alsobe made of radiolucent materials such as plastics, graphite, ceramicsand glass. The position encoders and force sensors associated with theactuators also can be made MR and/or X-ray imaging compatible. Forexample, fiber optic connected sine-cosine optical encoders, such as arecommercially available from MicroE, Renishaw or Computer OpticalProducts, can be used for the position encoding and piezoelectric straingauges for the force sensing.

From the foregoing, it will be appreciated that the present inventionprovides a lightweight and compact patient mountable manipulator thatcan be used in a master-slave robotic system to enhance the dexterity ofa operator/surgeon. The capability of fixing the manipulator relative tothe body of a patient provides enhanced safety by substantially reducingthe likelihood of trauma caused by unintentional movement of the patientrelative to the manipulator. Moreover, fixing the manipulator relativeto the body of the patient provides a very precise mechanical referencewhich facilitates tracking of the medical tool with respect to a pre-and/or intra-operative image. The manipulator can be constructed suchthat it can be operated while performing MR or X-ray imaging so as allowto the position of the tool to be referenced to a real-time or nearreal-time image. Thus, the lightweight, compact manipulator of thepresent invention and its capability of operating in up to six degreesof freedom in a relatively large workspace makes the invention suitablefor use in any number of different medical procedures including, forexample, neurosurgery, ear surgery, sinus surgery and spine surgery.

All of the references cited herein, including patents, patentapplications, and publications, are hereby incorporated in theirentireties by reference.

While this invention has been described with an emphasis upon preferredembodiments, it will be obvious to those of ordinary skill in the artthat variations of the preferred embodiments may be used and that it isintended that the invention may be practiced otherwise than asspecifically described herein. Accordingly, this invention includes allmodifications encompassed within the spirit and scope of the inventionas defined by the following claims.

1. A manipulator for use in performing medical procedures on a portionof a body of a patient, comprising: a medical tool; a positioningmechanism which carries the medical tool, the positioning mechanismbeing capable of moving the tool with at least one degree of freedom; amovable haptic interface that is adapted to receive manually inputposition information from an operator and which communicates with amanipulator controller that directs movement of the positioningmechanism; a remote position tracking system including anelectromagnetic field generator for producing a multidimensionalelectromagnetic field in three mutually distinguishable dimensions, theposition tracking system being capable of tracking the position of themedical tool and the body of the patient relative to a predeterminedframe of reference in three dimensions as the tool is moved by thepositioning mechanism, at least a portion of the remote positiontracking system being arranged remotely from the positioning mechanism.2. A manipulator according to claim 1 wherein the positioning mechanismcomprises first and second arms which pivotably support the medical tooland which are movable independently of each other.
 3. A manipulatoraccording to claim 1 wherein the haptic interface is adapted tocommunicate position signals based on the position information to themanipulator controller and the manipulator controller is adapted to makepredetermined adjustments to the position signals prior to directingmovement of the positioning mechanism.
 4. A manipulator for use inperforming medical procedures on a portion of a body of a patient,comprising: a medical tool; a positioning mechanism which carries themedical tool, the positioning mechanism being capable of moving the toolwith at least one degree of freedom; a movable haptic interface that isadapted to receive manually input position information from an operatorand which communicates with a manipulator controller that directsmovement of the positioning mechanism; a remote position tracking systemincluding an electromagnetic field generator for producing amultidimensional electromagnetic field in three mutually distinguishabledimensions, the position tracking system being capable of tracking theposition of the medical tool relative to a predetermined frame ofreference in three dimensions as the tool is moved by the positioningmechanism, at least a portion of the remote position tracking systembeing arranged remotely from the positioning mechanism; a first remotefield sensor carried by the tool for detecting the multidimensionalelectromagnetic field; and a second remote field sensor carried by thepositioning mechanism or the body of the patient for detecting themultidimensional electromagnetic field.
 5. A manipulator according toclaim 4 wherein the haptic interface is adapted to communicate positionsignals based on the position information to the manipulator controllerand the manipulator controller is adapted to make predeterminedadjustments to the position signals prior to directing movement of thepositioning mechanism.
 6. A manipulator according to claim 4 wherein thepositioning mechanism comprises first and second arms which pivotablysupport the medical tool and which are movable independently of eachother.